FreeBSD : xen-kernel -- x86: Mishandling of SYSCALL singlestep during emulation (942433db-c661-11e6-ae1b-002590263bf5)

Medium Nessus Plugin ID 95974


The remote FreeBSD host is missing a security-related update.


The Xen Project reports :

The typical behaviour of singlestepping exceptions is determined at the start of the instruction, with a #DB trap being raised at the end of the instruction. SYSCALL (and SYSRET, although we don't implement it) behave differently because the typical behaviour allows userspace to escalate its privilege. (This difference in behaviour seems to be undocumented.) Xen wrongly raised the exception based on the flags at the start of the instruction.

Guest userspace which can invoke the instruction emulator can use this flaw to escalate its privilege to that of the guest kernel.


Update the affected package.

See Also

Plugin Details

Severity: Medium

ID: 95974

File Name: freebsd_pkg_942433dbc66111e6ae1b002590263bf5.nasl

Version: $Revision: 3.4 $

Type: local

Published: 2016/12/21

Modified: 2017/01/31

Dependencies: 12634

Risk Information

Risk Factor: Medium


Base Score: 4.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:P


Base Score: 7.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:xen-kernel, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Patch Publication Date: 2016/12/20

Vulnerability Publication Date: 2016/12/19

Reference Information

CVE: CVE-2016-10013

IAVB: 2017-B-0008